Influence of Nitrogen Rate on Cercospora Leaf Spot and Growth of Crapemyrtle

2009 ◽  
Vol 10 (1) ◽  
pp. 2 ◽  
Author(s):  
A. K. Hagan ◽  
J. R. Akridge ◽  
K. L. Bowen

The impact of N rate on development of Cercospora leaf spot on field grown ‘Carolina Beauty’ crapemyrtle and the impact of this disease, as well as N rate, on plant growth was assessed in Alabama. From 2002 to 2005, ammonium nitrate was applied at an N rate of 2, 4.1, 8.3, 16.5, 33.0, and 66.0 g/m2. Heritage 50W fungicide was applied to one tree in each plot, while the second tree was not treated. Powdery mildew was very sporadic and was not related to N rate. An N rate-related reduction in Cercospora leaf spot intensity and defoliation was noted on the non-fungicide and fungicide treated trees in 2005 but not in 2003 and 2004. In 2005, reductions in disease intensity and defoliation were obtained at the three highest N rates of 16.5, 33, and 66 g/m2 compared to the two lowest N rates of 2 and 4.1 g/m2. Regardless of N rate, Heritage 50W suppressed Cercospora leaf spot. Despite considerable leaf spotting and premature defoliation, Cercospora leaf spot did not impact crapemyrtle growth. Increasing N rates was less effective than Heritage 50W fungicide in controlling Cercospora leaf spot and also failed to enhance tree growth. Accepted for publication 10 September 2009. Published 14 December 2009.

2008 ◽  
Vol 26 (4) ◽  
pp. 197-203
Author(s):  
A.K. Hagan ◽  
J.R. Akridge ◽  
K.L. Bowen

Abstract Impact of nitrogen (N) rate on spot anthracnose, powdery mildew, and Cercospora leaf spot as well as their impact on the growth of field-grown ‘Cloud 9’ and ‘Cherokee Chief’ flowering dogwood was assessed in 2003, 2004, and 2005. From 2001 to 2005, ammonium nitrate was applied at 4.1, 8.3, 16.5, 33.0 and 66.0 g N·m−2 (37.5, 75, 150, 300, 600 lb N·A−1). Heritage 50W fungicide was applied to one ‘Cherokee Chief’ and ‘Cloud 9’ flowering dogwood in each plot, while the second was untreated. Powdery mildew and Cercospora leaf spot were impacted by N rate more than spot anthracnose. In two of three years, powdery mildew intensified, particularly on the non-treated trees, as N rates increased. Cercospora leaf spot intensity (AUDPCI) and defoliation (AUDPCD) on the fungicide-treated and non-treated trees was influenced by N-rate in two of three and one of three years, respectively. Regardless of fungicide treatment, Cercospora leaf spot incited leaf spotting and defoliation was often lower at the two highest than the two lowest N rates. A reduction in the bract and leaf spot phases of spot anthracnose at the highest N rate was noted in 2004. While spot anthracnose was negatively correlated with trunk diameter in all three years and tree height in 2003 and 2004, Cercospora leaf spot intensity and defoliation were negatively correlated with tree height and trunk diameter in all three and two of three years, respectively. Powdery mildew had no impact on tree height or trunk diameter. Heritage 50W not only controlled spot anthracnose and powdery mildew but also slowed Cercospora leaf spot development sufficiently to enhance leaf retention and fall color.


2005 ◽  
Vol 23 (2) ◽  
pp. 77-85 ◽  
Author(s):  
A.K. Hagan ◽  
M.E. Rivas-Davila ◽  
J.R. Akridge ◽  
J.W. Olive

Abstract Reaction of selected shrub and ground cover roses to black spot, Cercospora leaf spot, and powdery mildew, as well as the impact of fungicide inputs on the control of the above diseases, was assessed from 1999 through 2003 in a simulated landscape planting in Brewton, AL. Chlorothalonil at 1.25 g ai/liter was applied at 2- and 4-week intervals from mid-March until October to randomly selected plants in each replicate. An unsprayed control was also included in each replicate. Although black spot was the predominate disease observed, a number of rose selections suffered from objectionable Cercospora leaf spot-induced leaf spotting and premature defoliation. Few mixed outbreaks of black spot and Cercospora leaf spot on a single selection were seen. In all years, significant differences in the reaction of rose selections to black spot and Cercospora leaf spot were noted. Of the roses damaged by black spot, the least leaf spot and defoliation were noted on the unsprayed Ice Meidiland®, Mystic Meidiland®, Red Cascade™, ‘Hansa’, ‘Pink Grootendorst’, ‘Pink Pet’, and to a lesser extent Carefree Wonder™ and Pearl Sevillana™. In a residential planting, monthly applications of chlorothalonil or other recommended fungicide would be needed to protect the above rose selections from a destructive black spot outbreak. ‘Betty Prior’, Bonica®, Cherry Meidiland®, First Light™, Kent™, Jeepers Creeper™, ‘Livin’ Easy™, Lilian Austin™, ‘Nearly Wild’, ‘Nozomi’, Butterfly rose, Ralph's Creeper™, Raven™, Royal Bonica™, ‘Sea Foam’, Sevillana™, and Sweet Chariot™ were susceptible to black spot. While black spot did not appreciably damage Carefree Delight™, Flower Carpet®, White Flower Carpet®, Fire Meidiland®, Fuchsia Meidiland®, Happy Trails™, ‘Petite Pink Scotch’, Polar Ice™, R. wichurana, The Fairy™, and ‘Therese Bugnet’, considerable Cercospora leaf spot development occurred on all of the above rose selections. Of these roses, Polar Ice™, Fuchsia Meidiland®, and Fire Meidiland® exhibited the highest resistance to Cercospora leaf spot and may not require any fungicide inputs to maintain plant health and vigor. Magic Carpet™ and Knock Out™ roses, which were susceptible and resistant to black spot, respectively, as well as Flower Carpet®, and White Flower Carpet® appeared to be poorly adapted to the hot and sometimes dry summer weather patterns of South Alabama. In nearly all years, chlorothalonil gave better control of both diseases when applied on a 2-week than on a 4-week schedule. Significant chlorothalonil-induced leaf burn was seen on First Light™, Flower Carpet®, ‘Hansa’, Happy Trails™, Magic Carpet™, Mystic Meidiland™, ‘Nozomi’, and Raven™. Consistent powdery mildew development was found only on ‘Therese Bugnet’ and to a lesser extent on Red Cascade™ and ‘Petite Pink Scotch’. Canopy spread of the roses that were heavily damaged by black spot and Cercospora leaf spot often was often reduced in size when compared with that of adjacent chlorothalonil-treated plants of the same selection. In contrast, little if any increase in growth was obtained with fungicide inputs for the more disease resistant rose selections.


2008 ◽  
Vol 43 (6) ◽  
pp. 781-782 ◽  
Author(s):  
Rogério Faria Vieira ◽  
José Eustáquio Souza Carneiro ◽  
Trazilbo José de Paula Júnior ◽  
Roberto Fontes Araújo

Mungbean cultivar MGS Esmeralda was developed by Asian Vegetable Research and Development Center (Shanhua, Taiwan), as a result of crossing between the lines VC 1973A and VC 2768A. In ten trials conducted in the State of Minas Gerais, Brazil, it produced 13.5% more grains than 'Ouro Verde MG-2' (control cultivar), and its highest yield was 2,550 kg ha-1. The cultivar MGS Esmeralda is more susceptible to lodging, and its pods mature more uniformly than Ouro Verde MG-2 pods. One hundred-seed mass of 'MGS Esmeralda' ranged between 5.5 and 6.8 g. Both cultivars are susceptible to powdery mildew and cercospora leaf spot.


2004 ◽  
Vol 22 (2) ◽  
pp. 58-62 ◽  
Author(s):  
A. K. Hagan ◽  
J. W. Olive ◽  
J. Stephenson ◽  
M. E. Rivas-Davila

Abstract Efficacy of azoxystrobin (Heritage 50W™) was assessed over a range of application rates and intervals for the control of powdery mildew (Erysiphe polygoni) and Cercospora leaf spot (Cercospora hydrangea) on bigleaf hydrangea (Hydrangea macrophylla) ‘Nikko Blue’. Rooted hydrangea cuttings were transplanted in a pine bark/peat mixture. In 1998 and 1999, azoxystrobin at 0.16 g ai/liter and 0.32 g ai/liter, as well as 0.24 g ai/liter myclobutanil (Eagle 40W™) and 0.84 g ai/liter thiophanate methyl (3336 4.5F™), greatly reduced the incidence of powdery mildew compared with the untreated control where 75% of the leaves of were infected by the causal fungus. When applied at 1-, 2-, and 3-week intervals, both rates of azoxystrobin were equally effective in both years in preventing the development of powdery mildew on bigleaf hydrangea. In 1998, all fungicides except for thiophanate methyl protected bigleaf hydrangea from Cercospora leaf spot. In the last two trials, the incidence of powdery mildew increased significantly as the application rate for azoxystrobin decreased from 0.16 to 0.04 g ai/liter and the application interval was lengthened from 1 to 3 weeks. In general, all rates of azoxystrobin applied on a 3-week schedule failed to provide the level of powdery mildew control needed to produce quality bigleaf hydrangea for the florist and landscape market. When applied at 2-week intervals, myclobutanil was equally or more effective in controlling powdery mildew than any rate of azoxystrobin applied on the same schedule. When compared to the untreated controls, significant reductions in the incidence of powdery mildew on bigleaf hydrangea were obtained with weekly applications of paraffinic oil. No symptoms of phytotoxicity were associated with the use of any of the fungicides screened.


Agronomy ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1930
Author(s):  
Emir Memic ◽  
Simone Graeff-Hönninger ◽  
Oliver Hensel ◽  
William D. Batchelor

A CSM-CERES-Beet pest damage routine was modified to simulate the impact of Cercospora leaf spot disease effects on sugar beet yield. Foliar disease effects on sugar beet growth and yield were incorporated as daily damage to leaf area and photosynthesis, which was linked to daily crop growth and biomass accumulation. An experiment was conducted in Southwest Germany (2016–2018) with different levels of disease infection. Data collected included time-series leaf area index, top weight, storage root weight and Cercospora leaf spot disease progress. The model was calibrated using statistical and visual fit for one treatment and evaluated for eight treatments over three years. Model performance of the calibration treatment for all three variables resulted in R2 values higher than 0.82 and d-statistics higher than 0.94. Evaluation treatments for all three observation groups resulted in high R2 and d-statistics with few exceptions mainly caused by weather extremes. Root mean square error values for calibration and evaluation treatments were satisfactory. Model statistics indicate that the approach can be used as a suitable decision support system to simulate the impact of observed Cercospora leaf spot damage on accumulated above-ground biomass and storage root yield on a plot/site-specific scale.


Plant Disease ◽  
2007 ◽  
Vol 91 (4) ◽  
pp. 470-470 ◽  
Author(s):  
C. A. Bradley ◽  
P. Burlakoti ◽  
R. S. Nelson ◽  
M. F. R. Khan

Powdery mildew caused by Erysiphe polygoni was widespread on sugar beet (Beta vulgaris) in North Dakota during 2006. This disease is generally not prevalent in the state because of the application of fungicides, which also have efficacy against powdery mildew, for control of Cercospora leaf spot caused by Cercospora beticola. Because Cercospora leaf spot pressure was low in 2006, fewer fungicide applications were made in the state, thus allowing for more observations of powdery mildew. Leaf samples from four fields near Amenia, Minto, Prosper, and St. Thomas, ND were collected in mid-September to look for the perfect stage of E. polygoni, since this has recently been observed in Idaho, Colorado, Montana, and Nebraska (1–3). Only the leaves collected from the field near Amenia had visible immature (yellow and brown) globose ascomata; ascomata were not observed on the leaves collected in the other fields. Additional leaves were collected from the field near Amenia in early October; these leaves had immature and mature (black) globose ascomata that were 70 to 105 μm in diameter. Mature ascomata contained ovoid to elliptic asci with one to four hyaline-to-golden pigmented ascospores (20 to 25 × 12 to 20 μm). The color, shape, and size of ascomata, asci, and ascospores were similar to previously reported observations (1–4). The prevalence of the perfect stage in North Dakota is unknown, since no statewide surveys were conducted. To our knowledge, this is the first report of the perfect stage of E. polygoni on sugar beet in North Dakota. The occurrence of the perfect stage could lead to a means for overwintering in this area. Because of the means for genetic recombination, the risk of fungicide resistance and the development of races may increase. References: (1) J. J. Gallian and L. E. Hanson. Plant Dis. 87:200, 2003. (2) R. M. Harveson. Plant Dis. 88:1049, 2004. (3) B. Jacobsen et al. Plant Dis. 89:1362, 2005. (4) E. G. Ruppel. Powdery mildew. Pages 13–15 in: Compendium of Beet Diseases and Insects. E. D. Whitney and J. E. Duffus, eds. The American Phytopathological Society. St. Paul, MN, 1986.


2011 ◽  
Vol 29 (4) ◽  
pp. 169-174
Author(s):  
A.K. Hagan ◽  
J.R. Akridge ◽  
J. Ducar ◽  
K.L. Bowen

Abstract Stellar® dogwood (Cornus florida × kousa) cultivars Aurora®, Constellation®, Celestial™, Ruth Ellen®, and Stellar Pink® were compared with selected flowering dogwood (Cornus florida) cultivars Cherokee Brave®, ‘Cherokee Princess’, ‘Cloud 9’, and ‘Rubra’ in a simulated landscape planting at sites in southwest (USDA Hardiness Zone 8a) and northeast Alabama (USDA Hardiness Zone 7a) for their reaction to the diseases spot anthracnose, powdery mildew, and Cercospora leaf spot. Tree longevity as influenced by the occurrence of the dogwood borer (Synanthedon scitula) and an ambrosia beetle (Xylosandrus sp.) was also assessed at both sites. All Stellar® dogwood cultivars generally proved resistant to the bract and leaf spot phases of spot anthracnose as well as powdery mildew and Cercospora leaf spot. While Cherokee Brave® was the only flowering dogwood with partial resistance to powdery mildew at both sites; this and the other flowering dogwood cultivars were equally susceptible to spot anthracnose and Cercospora leaf spot. Insect damage levels were higher at the southwest site than the northeast Alabama site. Within 3 years of establishment at the southwest Alabama site, incidence of tunneling damage attributed to dogwood borer and an ambrosia beetle was higher on the Stellar® dogwood than flowering dogwood cultivars, which also had higher values for tree longevity. In contrast, tree longevity was equally high and insect damage equally low at the northeast Alabama site for both the Stellar® and flowering dogwood cultivars. Superb resistance to the diseases spot anthracnose, powdery mildew, and Cercospora leaf spot translated into superior aesthetics and fall color for the Stellar® compared with the flowering dogwood cultivars at the northeast Alabama site. Hardiness of Stellar® dogwood cultivars in Alabama and possibly other southern states below USDA Hardiness Zone 7a is questionable due to tree vulnerability to the dogwood borer and ambrosia beetle.


Author(s):  
Yu Yu Min ◽  
Koki Toyota

We surveyed diseases of sesame in 10 farmers’ fields at Nay Pyi Taw, Myanmar and did interviews 25 farmers for the occurrence of diseases and its impact on yield in Magway, the major sesame growing area in Myanmar. We found phyllody, charcoal rot (root and stem rot), Alternaria leaf blight, powdery mildew, and leaf curl, based on on-site symptoms and their microscopic observation in Nay Pyi Taw. The disease incidence ranged from 5% to 30% in phyllody, from 10% to 30% in charcoal rot (root and stem rot) and 10% to 40% in Alternaria blight, while leaf curl and powdery mildew were not observed abundantly. According to interviews conducted in Magway, 60% of the farmers suffered from phyllody disease symptoms, 80% from charcoal rot, 48% from Cercospora, 28% bacterial leaf spot and 24% diseases with the symptoms of leaf roll. Most farmers (84%) noticed combinations of diseases symptoms either phyllody or charcoal rot/black and stem rot or Cercospora leaf spot and/or bacterial leaf spot. Yield losses ranged from 5 to 50% by phyllody, from 10 to 75% by charcoal rot (root and stem rot), from 5 to 50% by Cercospora leaf spot, and 5% by bacterial leaf spot. Other abnormal symptoms such as discoloring of root, seedling death and leaf yellowing were also observed and the yield losses ranged from 5 to 50%.There were no significance relations between the actual yield and yield losses estimated by each disease. A half of farmers (54%) burnt the crop residues after harvest, while 45% directly buried them in their fields including plant parts infected with diseases. Although there was no difference in sesame yield between these two practices, the average yield was higher by 15% in farmers with the burnt practice. Only a few farmers applied fungicides. Potential constraints to cause yield reduction and necessary actions to increase sesame yield are discussed.


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